Rodolfo A. Coria

THE BRAINCASE OF GIGANOTOSAURUS CAROLINII(DINOSAURIA: THEROPODA) FROM THE UPPER CRETACEOUS OF ARGENTINA

Abstract Giganotosaurus carolinii is one of the largest known theropod dinosaurs. Its remains include a well-preserved braincase that displays a suite of derived characters unique to the animal, and others that help establish its relationships amongst the Theropoda. These include the development of a broad frontoparietal skull table that forms a shelf overhanging the supratemporal fenestra, the reorientation of the metotic fissure and fenestra ovalis onto the occiput, the ventral extension of the supraoccipital on either side of the foramen magnum, a broad but low occipital condyle, and pneumatization of the basioccipital. Some characters suggest affinities with South American abelisaurids, but many support a sister grouping of Giganotosaurus and Carcharodontosaurus within a larger group that includes the Asian sinraptorids. The close affinities of Giganotosaurus with the northern African Carcharodontosaurus support the hypothesis of intercontinental connections until mid-Cretaceous times.

The first record of a sauropod dinosaur from Antarctica

Sauropoda is one of the most diverse and geographically widespread clades of herbivorous dinosaurs, and until now, their remains have now been recovered from all continental landmasses except Antarctica. We report the first record of a sauropod dinosaur from Antarctica, represented by an incomplete caudal vertebra from the Late Cretaceous of James Ross Island. The size and morphology of the specimen allows its identification as a lithostrotian titanosaur. Our finding indicates that advanced titanosaurs achieved a global distribution at least by the Late Cretaceous.

March of the Titans: The Locomotor Capabilities of Sauropod Dinosaurs

Sauropod dinosaurs are the largest terrestrial vertebrate to have lived on Earth. This size must have posed special challenges for the musculoskeletal system. Scaling theory shows that body mass and hence the loads that must be overcome increases with body size more rapidly than either the ability of the muscles to generate force, or the ability of the skeleton to support these loads. Here we demonstrate how one of the very largest sauropods, Argentinosaurus huinculensis (40 metres long, weighing 83 tonnes), may have moved. A musculoskeletal model was generated using data captured by laser scanning a mounted skeleton and assigning muscle properties based on comparative data from living animals. Locomotion is generated using forward dynamic simulation to calculate the accelerations produced by the muscle forces, coupled with machine learning techniques to find a control pattern that minimises metabolic cost. The simulation demonstrates that at such vast body size, joint range of motion needs to be restricted to allow sufficient force generation for an achievable muscle mass. However when this is done, a perfectly plausible gait can be generated relatively easily. Whilst this model represents the best current simulation of the gait of these giant animals, it is likely that there are as yet unknown mechanical mechanisms, possibly based on passive elastic structures that should be incorporated to increase the efficiency of the animals locomotion. It is certainly the case that these would need to be incorporated into the model to properly assess the full locomotor capabilities of the animal.

Embryonic skin from Late Cretaceous Sauropods (Dinosauria) of Auca Mahuevo, Patagonia, Argentina

Abstract We describe the integumentary anatomy of titanosaur sauropod embryos from the Auca Mahuevo nesting site. Natural (calcitic) casts of the skin show the non-imbricating, tuberculate scales (i.e., tubercles) typical of other non-avian dinosaurs. However, a variety of scale patterns previously unknown for the skin of these animals is reported. The observed integumentary patterns include ground tubercles, large and elongated tubercles, parallel rows of large tubercles, tubercles in rosette-like and flower-like arrangements, and in striate-like rows. Ground tubercles and rosette-like patterns resemble the few examples of skin known for adult sauropods. The former pattern also resembles the arrangement of osteoderms of the armored titanosaur Saltasaurus. Although the embryonic skin does not show definitive evidence of armor, the posthatching development of osteoderms cannot be ruled out. This material, the only available evidence of the embryonic skin of non-avian dinosaurs, contributes significantly to our knowledge of the integumentary morphology of these animals.

Un nuevo hadrosáurido (Dinosauria, Ornithopoda) de la Formación Allen, Provincia de La Pampa, Argentina

Abstract. A NEW HADROSAURID (DINOSAURIA, ORNITHOPODA) FROM ALLEN FORMATION, LA PAMPA PROVINCE, ARGENTINA. New studies of a Hadrosauridae specimen collected in the Allen Formation, Late Campanian/Early Maastrichthian from La Pampa Province, Argentina, allow recognizing a new taxon, Lapampasaurus cholinoi gen. et sp. nov., which is diagnosed by the following combination of characters: anterior cervical vertebrae with lateral foramina on the dorsal side of the diapophyses, scapula with laterally sharp deltoid crest and convex dorsal surface, pedal ungual phalanx longer than wide with superficial grooves and foramina, and shallow, longitudinal ventral ridge. The identification of Lapampasaurus as a member of Hadrosauridae is confirmed by the recognition of several synapomorphies, such as cervical neural arches with zygapophysial peduncles that elevate above the neural canal, long and dorsally arched postzygapophyses, coracoid relatively small when compared with the scapula, with concave anterior margin and well developed bicipital knob, and hoof-shaped pedal ungual phalanx. The record of Lapampasaurus in the Late Cretaceous of Patagonia suggests the presence of a more diverse hadrosaurid fauna than previously recorded.

Palaeopathological Survey of a Population of Mapusaurus (Theropoda: Carcharodontosauridae) from the Late Cretaceous Huincul Formation, Argentina

Paleoepidemiology (the study of disease and trauma in prehistoric populations) provides insight into the distribution of disease and can have implications for interpreting behavior in extinct organisms. A monospecific bonebed of the giant carcharodontosaurid Mapusaurus (minimum number of individuals = 9) from the Cañadón del Gato site, Neuquén Province, Argentina (Cenomanian) provides a rare opportunity to investigate disease within a single population of this important apex predator. Visual inspection of 176 skeletal elements belonging to a minimum of nine individuals yielded a small number of abnormalities on a cervical vertebra, two ribs, pedal phalanx, and an ilium. These are attributed to traumatic (two cases), infectious (two cases) and anomalous (one case) conditions in a minimum of one individual. The emerging picture for large theropod (abelisaurids, allosaurids, carcharodontosaurids, tyrannosaurids) populations suggests that 1) osseous abnormalities were relatively rare (7–19% of individuals) but consistently present, and 2) trauma was a leading factor in the frequency of pathological occurrences, evidence of an active, often perilous lifestyle.

Osteología embrionaria de saurópodos titanosaurios de Neuquén (Argentina): aspectos ontogenéticos y evolutivos

Abstract Embryonic osteology of titanosaur sauropods from Neuquén (Argentina): ontogenetic and evolutionary considerations. Titanosaur embryonic remains are described from megaloolithid eggs collected in the Anacleto Formation (Late Cretaceous) at Auca Mahuevo in Neuquén province (Argentina). These remains include complete articulate and disarticulate skulls, and numerous cranial and appendicular isolated elements. The embryonic skull is short, high, and presents numerous fenestrae, most of which are known in adult titanosaurs. However, the morphology of the maxilla and jugal is very different from that of adult titanosaurs. These elements show a series of processes that arise from their central body, which seem to have become reduced and transformed during ontogeny. The dental formula (Pm4 M7-8 /D10?) is similar to that of known adult titanosaurs. Detailed osteological study of these remains shows features of taxonomic, phylogenetic, and evolutionary significance. Several of the characters, including the snout with “stepped” anterior margin and the infratemporal fenestra extending ventrally to the orbit support the identification of the embryos as eusauropods. Other characters, such as the absence of crown denticles and the presence of a preantorbital fenestra are considered to be synapomorphies of Neosauropoda. Finally, the posteriorly wide skull and a maxillary notch at the ventral margin of the skull are regarded as synapomorphies of Titanosauria. Characters such as relatively large orbit, short rostral portion of the skull, long alveolar rows, “egg tooth”, tooth crowns lacking wear facets, frontal occupying practically the entire dorsal margin of the orbit, and nonossified postcranial axial skeleton are typical characters of sauropod embryonic and juvenile stages.

Restos de Alvarezsauridae (Theropoda, Coelurosauria) en la Formación Alien (Campaniano-Maastrichtiano), en Salitral Ojo de Agua, Provincia de Río Negro, Argentina

Remains of Alvarezsauridae (Theropoda, Coelurosauria) in the Allen Formation (Campanian- Maastrichthian), in Salitral Ojo de Agua, Rio Negro Province, Argentina. We present new remains from the Cam- panian-Maastrichtian beds of the Allen Formation, in Salitral Ojo de Agua (Rio Negro, Argentina), which are assignable to Alvarezsauridae indet. This clade of small coelurosaurian theropods is known from strata of similar age in Mongolia, and from older sediments (Turonian and Coniacian in age) in Argentina. Thus, the material presented here extends the temporal record of the alvarezsaurids from the Southern Hemisphere up to the Latest Cretaceous. The fossil bones reported were associated to eggshells of the oofamily Elongatoolithidae, which are actually attributed to Theropoda.

Cranial ontogenetic variation in Mapusaurus roseae (Dinosauria: Theropoda) and the probable role of heterochrony in carcharodontosaurid evolution

The carcharodontosaurid theropod Mapusaurus roseae (Cenomanian of Neuquén Province, Argentina) is represented by at least seven disarticulated individuals from a monospecific bonebed, all of different sizes and presumably different stages of maturity. We report a series of anatomical differences between repeated skull bones of Mapusaurus, which we interpret as produced by peramorphic heterochronic processes. The materials analyzed include maxillae, lacrimals, dentaries, and isolated teeth. Most of the differences were recorded in the maxilla, the most noticeable change being the reduction of the pneumaticity. We found that some of the synapomorphic characters of derived carcharodontosaurids appear to be the result of peramorphic heterochronies, as in the strongly ornamented facial bones, and the single opening in the anteroventral corner of the antorbital fossa in the maxilla.KurzfassungDer carcharodontosauride Theropode Mapusaurus rosae (aus dem Cenoman der Provinz Neuquén, Argentinien) ist durch mindestens 7 disartkulierte Individuen verschiedener Größe und vermutlich unterschiedlicher ontogenetischer Stadien aus einem monospezifischen Bonebed repräsentiert. Wir beschreiben eine Reihe anatomischer Unterschiede zwischen mehrfach vorkommenden Schädelknochen von Mapusaurus, die wir als Ergebnis peramorphischer Heterochronie-Prozesse interpretieren. Die untersuchten Elemente umfassen Maxillae, Lacrimale, Dentale und isolierte Zähne. Die größten Änderungen finden sich im Maxillare, wobei besonders die Reduktion der Pneumatisierung auffällt. Wir stellen fest, dass einige der apomorphen Merkmale fortschrittlicher Carcharodontosauriden auf Heterochronie zurückzuführen sind, darunter die stark ornamentierten Schädelknochen und das Vorhandensein nur einer Öffnung im anteroventralen Teil der Fossa antorbitalis im Maxillare.

Late Cretaceous dinosaurs from the James Ross Basin, West Antarctica

Abstract The fossil record of terrestrial vertebrates from the Late Cretaceous of Antarctica is currently composed of non-avian and avian dinosaurs from the marine sediments of the James Ross Basin, Antarctic Peninsula (West Antarctica). Although two dinosaurian formational assemblages (Late Campanian/Early Maastrichtian and Late Maastrichtian) are known, the record is still scattered, and evolutionary scenarios are tentative. Ten non-avian dinosaurs have been reported from Coniacian to Maastrichtian deposits, along with possible sauropod footprints of Early Maastrichtian age from Snow Hill Island. Five avian dinosaurs have been recorded or described exclusively from the Maastrichtian. The presence of an advanced titanosaur with characteristic procoelous mid-caudal vertebrae in Snow Hill Island Formation at Santa Marta Cove implies that the group achieved a global distribution by the Late Campanian. The Late Campanian/Early Maastrichtian non-avian dinosaur (ankylosaurs, ornithopods and dromaeosaurid theropods) clades probably attained a near-cosmopolitan distribution before the Late Cretaceous, and some aspects of this hallmark ‘Gondwanan’ fauna may therefore reflect climate-driven provinciality, not vicariant evolution driven by continental fragmentation. Antarctic Late Cretaceous avian dinosaurs are rare. They are restricted to the Maastrichtian and consist of a cariamid?, gaviids, a charadriiform and the basal Anseriformes Vegavis, and provide the first strong evidence for a basal radiation of birds known to exist in the Cretaceous.